One hot spot for health care fraud is Los Angeles, California, where Russian, Armenian and Nigerian gangs have been caught by federal agents.

Recent cases include crime boss Konstantin Grigoryan, a former Soviet army colonel who pleaded guilty to taking $20 million from Medicare. Karapet "Doc" Khacheryan, boss of a Eurasian crime gang, was recently convicted with five lieutenants of stealing doctor identities in a $2 million scam.

Two Nigerians, Christopher Iruke and his wife, Connie Ikpoh, were charged October 15 with bilking Medicare of $6 million dollars by fraudulently billing the government for electric wheelchairs and other expensive medical equipment.

The two, allegedly members of anorganized crimering, entered pleas of not guilty and are being held in a federal detention center. "They deny any allegations of wrongdoing," said their attorney, James Kosnett.

Defrauding government-run health care programs involves stealing two types of identities: those of doctors, who bill for services, and patients, whose beneficiary numbers entitle them to medical care and necessary equipment. Criminals are expert at collecting both.Watch doctor tell what happened when his identity was stolen »